RGP fabrication or BC measurement error

Two weeks ago a doctor with her lab fabricated
a RGP contact lens with requested specs of -8.0
diopter, 7.85 base curve and 9mm. When I brought
the lens to the laboratory for specification
yesterday (because the image was not sharp). It
was reported the base curve is 7.7. This brings me to
these questions.

1. Supposed their Base Curve measuring devices are
NOT accurate and can't tell difference between 0.15 base
curve. What kind of instruments is that? They won't reveal
it saying it is confidential. Is it plain keratometry (can
this directly read RGP lens) or is it the radiuscope (or
others?)?

2. Supposed their measuring devices are accurate
and the fabrication is NOT accurate producing 7.7
from required 7.85 base curve. What kind of machine
error can do it? Does RGP fabrication requires yearly
replacement of some parts such as diamond cutter
for example??

3. Can you really produce a RPG down to the correct
7.85 base curve or is it 7.8 or 7.9 only rounding off??


kyle

 

Kyle,

There is one person who is capable to measure and
decide if your lens is correct made or not and that is your fitter.
And you decide if you are satified and if not have to complain at your the
manufactor with the help of a paper written by your fitter what is wrong in
his/her opinion
You are turning around in circles.
You have a lot of questions and postings here.
It looks like you do not read the answers carefully and you do not respond
when you get an answer (except for your first posting where you respond with
a new question)
In this way you might get no answers anymore.

Jan (normally Dutch spoken)

 

Jan,

I parted ways with my fitter. She said her contact lens are perfect
and she couldn't explain why I couldn't see clearly in the new lens
compared to the old ones. She said I may have to wait for 6 months
to adjust (and see if I can see clearly). When I let other labs
test the contacts. It is not according to the specs and the base
curve she ordered (7.7 versus the 7.85 she said she did). And she
didn't want to admit saying that even telling customers base curve
are not allowed and confidential and only their laboratory can hold
the information.

This is why I am asking questions here to enable me to decide what
is really wrong. I visited a second eye doctor and she said she
can't make the original 7.85 base curve because his lab only
makes 7.8 base curve. I let him made one. And the second RGP lens
is not sharp again. And he said there is nothing he can do.
So I wonder if laboratory can make the exact 7.85 or they have
to round it off to 7.8 ot 7.9. If you don't know the answer to
this. Hope others can help.

I want to figure out if their fabrication machine is up to spec
or if their product varies from + and - 0.1 base curve. Is this
possible? RGP lens is not in demand and they may not upgrade
their machine. I don't know. Or their measuring device may just
be simple hence they can't determine their own products base
curve.

I wasted 2 contact lens and they don't want to refund so I want
to make sure the third contact lens would be perfect (and I have
to know what is really wrong and only the experiences of folks in
this group can help).

kyle

 

Did you tell the doc that it just wasn't sharp or just start asking the
lab questions? When I was trying to get RGPs the guy ordered eight
different sets before he figured there was no way I could be fit with
RGPs due to the nature of my astigmatism. Surely you get more than one
chance for the doc to get it right...

--
Cheers, Bev
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
"I love to go down to the schoolyard and watch all the
little children jump up and down and run around yelling and
screaming...They don't know I'm only using blanks." --Emo

 

[/QUOTE]
over and over again..........text deleted

We've been all over the possibilities with this person. A number of us.
Either he/she has not read the responses, does not understand them, or
is looking for more excuses, but the information as to: 1, the WHY and
2. the way to RESOLVE have already been clearly presented.

-LB

--
Dr. Larry Bickford, O.D.
Family Practice Eye Health & Vision Care

The Eyecare Connection
http//www.eyecarecontacts.com
larrydoc at eye-care-contacts dot com (remove -)

 

over and over again..........text deleted

We've been all over the possibilities with this person. A number of us.
Either he/she has not read the responses, does not understand them, or
is looking for more excuses, but the information as to: 1, the WHY and
2. the way to RESOLVE have already been clearly presented.

-LB[/QUOTE]

I live in Asia. Here there are only 2 labaratories in the entire
country, and the eye doctors keep the base curve information
confidential. In fact, I have to force them to give me the base
curve information. In the U.S. Base curve is a normal thing and
most patient know it. But here, it is like top secret and only those
who earn a degree in opthalmology are supposed to understand it.
They also say they don't have access to the laboratory (which they
just ordered) so they can't know what instruments are used to measure
them. Now the first doctor told me to wait for months to know if
the lens is the right fit (Yes they know that it is not sharp in
my eyes compared to the original created a year ago which is perfect.
The second doctor said they don't fabricate 7.85 BC but just
7.8 and when he sent the first lens for testing at the
same lab. The result is 7.7. Now there is something obviously
wrong with the laboratory testing or fabrication method
and I want to understand the exact details so as to know what is
the best course of action to do which may include designing my
own lens or adjusting the parameters. I have already wasted 2
lens and don't want to repeat the same with the third. If
you guys refuse to answer in detail as this may jeopardize
your Opthalmology Secrecy Act (if there is one). Just
refer me to a book title that explains RGP lens fabrication and
testing in details. Thanks to those who can help.

kyle

 

Geez, Kyle. No one has refused to answer your questions. There's no
"secrecy act" and we gave you all sorts of information. So let's
review, for the very last time:

1.If you need a,for example, a lens with a 7.85mm base cure, 9.0
diameter lens with a power of -8, then that is exactly what should be
ordered and exactly what you should receive. Anything else is wrong.

2. The center thickness needs to specified to assure the lens does not
flex/warp on the eye, and (for those interested readers) that becomes
more and more important with increasing minus powers and for certain RGP
plastics.

3. Labs and anyone else who wants to verify parameters use radiascopes
for base curve, center thickness gauges for that, and a magnifier with
metric measuring redicule to measure diameter or a slot gauge.

4. If , with lens #1 you can see well and it is comfortable, and with
lens #2 it is not, then lens #1 is not the same as lens #2.

5. Lenses are lathe cut from "buttons" of the plastic material. We set
up the lathe's computer to turn the button into the desired parameters.
Good, calibrated lathes do just that. A quality lab will verify that
what was requested of the lathe did occur before sending it out.

6. If lens #2 does not perform as lens #1, then lens #2 is not the same
parameters.

Is there anything we missed or have not said repeatedly?

I'm sorry you are not getting quality service from your contact lens
paractitioner, but repeating the same query over and over again here has
gotten you the same responses, and now we are done. I do hope you can
resolve your problem, but it wont happen in this forum.

--LB

--
Dr. Larry Bickford, O.D.
Family Practice Eye Health & Vision Care

The Eyecare Connection
http//www.eyecarecontacts.com
larrydoc at eye-care-contacts dot com (remove -)